The present invention relates to an arrester holder apparatus for detachably mounting a plurality of arresters in a cassette type insulating support. More particularly, the present invention relates to an arrester holder apparatus applied to apparatus for protecting a plurality of circuits against a surge voltage and/or current, wherein the cassette type insulating support is detachably mounted in a distributor of a communication apparatus such as a telephone exchange, and the plurality of arresters are respectively connected to the plurality of circuits to be protected, such as transmission lines connected to the distributor.
A conventional arrester holder apparatus used in a distributor of a communication apparatus such as a telephone exchange comprises a plurality of contact members and a ground member. The plurality of contact members are partially embedded in a cassette type insulating support which is detachably mounted in the distributor. When the insulating support is mounted in the distributor, one contact portion of each of the plurality of contact members is connected to a corresponding terminal of the respective circuits to be protected. The terminals of the circuits to be protected are connected to the distributor. The other contact portion of each of the plurality of contact members is connected to one electrode of each of the plurality of arresters respectively mounted in arrester shells. The arrester shells are formed in the insulating support. The ground member is detachably mounted on the insulating support such that each of the contact pieces of one contact portion of the ground member opposes the other contact of each of the plurality of contact members and such that it is connected to the other electrode of each of the plurality of arresters. Each of the other contact portions of the ground member is commonly grounded. In the arrester holder apparatus of this type, when the number of arresters increases, the construction of the plurality of contact members becomes complicated. In this case, in order to simplify the construction of the plurality of contact members, a method for manufacturing contact members is proposed as described in Japanese Patent Publication No. 55-13370. According to this method, a single plate is punched to make an integral member consisting of contact members, the number of which is equal to that of the arresters, and transverse connecting bands connecting the contact members. This integral member is partially embedded in a cassette type insulating support by integral molding. Thereafter, the connecting portions of the transverse connecting bands are cut by a cutting tool to obtain a plurality of contact members. In the same prior art, a U-shaped common ground member is used to form a groove, and a notch is formed in one leg thereof. This notch is engaged with a projection formed on the cassette type insulating support, thereby detachably mounting the common ground member on the insulating support. At the same time, a plurality of contact pieces corresponding to the number of arresters is formed on the other leg of the common ground member such that the contact pieces are mounted in the arrester shells of the insulating support so as to respectively oppose the contact portions of the plurality of contact members. The respective arresters are detachably mounted in the gaps respectively formed between the contact pieces of the common ground member and the contact portions of the contact members, thereby electrically connecting the contact pieces of the common ground member with the contact portions of the contact members respectively through the arresters.
In an arrester holder apparatus of the type described above, as described in Japanese Patent Publication No. 55-13370, the axial direction (direction in which a pair of electrodes of the arrester oppose each other) of each arrester mounted in the corresponding arrester shell of the cassette type insulating support is perpendicular to the plane of the cassette type insulating support. Therefore, in the conventional apparatus, when the arresters are respectively mounted in the arrester shells or removed therefrom, the common ground member must be removed from the cassette type insulating support. Alternatively, the contact pieces of the common ground member must be forcibly opened, resulting in cumbersome operation. Furthermore, as the mounting/dismounting operation is repeated, the common ground member becomes deformed, and the engagement between the common ground member and the insulating support of the contact members becomes unstable. Consequently, the electrical contact between each contact member and the corresponding arrester becomes poor. In addition to the drawbacks described above, when the arrester holder apparatus is inserted into or removed from the distributor or the like, slidable operation therebetween cannot be smoothly performed. The electrical contact among the contact pieces of the ground member, the contact portions of the contact members, and the terminals (of the circuit to be protected) mounted in the distributor may not be properly performed.
Furthermore, in the type of arrester holder apparatus described above, the arresters mounted in the arrester shells of the cassette type insulating support are linearly aligned along the longitudinal direction of the cassette type insulating support. Therefore, the length of the insulating support must exceed a product obtained by multiplying the length of the arrester and the number of arresters. As a result, a compact arrester holder apparatus with a high density cannot be obtained, and the distributor connected thereto thus cannot be made compact.